Live USB will only boot from UEFI

Question

I have a 5 year old Toshiba Satellite L745. I wanted to install Ubuntu on it. It only has legacy BIOS and no UEFI. When I attempt to boot from a flash drive (I tested 2 flash drives and both worked on my desktop with UEFI) I received the error: "Missing operating system". I've installed it several different ways (ddrescue, Startup Disk Creator, Gnome Disk Utility, Unetbootin) and it won't work. The only thing I can get to boot is MATE and that is what is on it right now, but if I could, I'd prefer Ubuntu or Kubuntu. I've done a lot of googling and still can't seem to find the answer, so if anyone has any ideas, it would be appreciated

Edit: It seems that Ubuntu 15.10 has no legacy BIOS support? Because the result of fdisk -l labels it as an "EFI system". The output for the flash drive:

`Device        Start       End   Sectors   Size Type
 /dev/sdc1      2048  15628287  15626240   7.5G EFI System`

Update: I've made progress(?). Using the Startup Disk Creator on Ubuntu, I managed to get the following message when trying to boot:

SYSLINUX 6.03 EDD Copyright(etc...)
Boot error

Another update: I figured it out. I posted an answer down below. I can't accept it for 22 hours though.

Answer 1

I can think of three likely causes of your problem:

• An incorrectly-prepared boot medium -- To create a bootable USB flash drive from a .iso file, a utility must be able to write an appropriate boot loader to the drive. As EFI and BIOS require different boot loaders, it's now entirely possible to create a USB drive that will boot with one type of firmware but not the other, which could explain why you can boot the disk on an EFI-based computer but not on your older BIOS-based machine. If this hypothesis is correct, using different options with your utility, or a different utility entirely, may overcome the problem. For a BIOS-based boot, I'd say that a simple dd operation is the most likely to succeed. In a working Linux installation, use sudo dd if=imagefile.iso of=/dev/sdc bs=4096 to create a bootable USB flash drive on /dev/sdc. (Of course, you should adjust both imagefile.iso and /dev/sdc to suit your source and destination. Note that the destination must be a whole-disk device like /dev/sdc, not a partition.)
• A failure to use the computer's built-in boot options -- When you insert the USB drive in the computer on which you want to install Ubuntu, you must know how to get to your boot options menu. Normally this menu appears if you hit Esc, Enter, or a function key (typically F8 or above) soon after powering on. Sometimes you'll see a prompt about which key to use, but sometimes there is no prompt. In the latter case, you can guess -- try each possibility in turn. If nothing else works, you can adjust the boot order using the firmware setup utility.
• An incompatible USB drive -- I've encountered some USB flash drives that fail to work as BIOS-mode boot devices, although they work fine as ordinary data drives. I don't know why this is the case. If neither of the preceding two points helps, you might try a different brand of USB flash drive.

If all of the preceding suggestions fail, you might try burning an optical disc, assuming your computer has an optical drive. These sometimes work more reliably than a USB flash drive.

Answer 2

Ok, I solved it and here's how:

So basically I managed to get a Syslinux error when trying to boot instead of just a "missing operating system" when I used the Startup Disk creator. This obviously lead me to believe it was a problem with syslinux. I also knew that Ubuntu MATE would boot. So what I did was took two partitions on an external hard drive (you can do this with a single flash drive too) and, using the Startup Disk Creator, installed Kubuntu on one and MATE on the other. Then I went into the syslinux folder on the Kubuntu partition and copied all the .cfg files and pictures (.pcx, .jpg, .png) and put them in a folder on another hard drive. Once those were safe, I deleted the syslinux and boot folders. Then, I went to the MATE partition and copied those two folders from the MATE partition to the Kubuntu partition. Lastly, I copied the .cfg files and pictures and replaced the ones in the syslinux folder that I had just pasted on the Kubuntu partition. I got the gfxboot-com32-whatever (solution for that here) and then it booted right up!